Drying oils for bronzing inks



Patented Dec. 3, 1935 UNITED STATES PATENT I OFFICE 2,022,974. DRYING OILS FOR BRONZING INKS,

No Drawing. Application December 16, 1931, Serial N0. 581,507

1 Claim.

This invention relates to drying oils suitable for use in printing inks and the like.

More specifically this invention relates to drying oils prepared from rosin and softening agents to be used in the manufacture of printing inks of the bronzing variety.

Certain drying oils such as China-wood oil or those produced by decomposition of rosin or by polymerization of terpenes, when used for the manufacture of bronzing inks (those inks which possess a metallic, golden or bronze sheen when printed upon smooth or calendered paper) produce peculiar effects. In the preparation of bronzing inks, linseed oil has heretofore been used as a vehicle for the ink paste and. as a drying oil. It has been proposed to substitute other drying oils, such as those indicated above for the linseed oil. However, when these oils are used as a vehicle for the ink paste, the printed ink exhibits areas of no sheen under certain conditions.

It is therefore an object of this invention to produce novel drying oils which can be obtained from cheap initial material-and which may be used as linseed oil substitutes in bronzing inks without introducing the diificulties of unequal bronzing.

Another object of our invention is to provide a process to reduce or completely eliminate the objectionable unequal bronzing qualities which are characteristic of many drying oils, particularly rosin drying oils, when used for the manufacture of printing inks of the bronzing variety.

Other and further important objects of this invention will become apparent as the description proceeds.

The peculiar effect of inks which exhibit areas of no sheen when printed is best shown if prints are made having relatively large areas of ink and the printed sheets when taken off the press are stacked in an imperfectly superimposed manner. In this way, printed areas are placed over areas that are not inked. When the sheets are dry, all the inked areas below the top sheet show two tones. The areas which had no inked surfaces above them are bronzed, while the areas that had been covered by inked surfaces above them have a deeper non-bronzed tone.

Our investigations have shown that the unequal bronzing characteristics are due to a more or less brittle resinous film resulting from the drying oil ink vehicle as distinguished from a. flexible film resulting from a more expensive drying oil, such as linseed oil. A large number of well known drying oils, such as rosin oils, synthetic resins and polymerized terpenes dry to a somewhat brittle resinous film and are therefore inferior to the more expensive linseed oil.

We have discovered that the peculiarity of all oils which have the effect of drying to a more 5 or less brittle resinous film can be readily and efiiciently overcome, so as to make them perfectly adapted for the manufacture of bronzing inks. By means of our discovery, we are therefore able to use cheaper drying oils in place of linseed oil. We accomplish the result of adapting the inferior cheaper oils to the manufacture of bronzing inks by adding to them small amounts of certain materials which act as softening agents to the dry film. The amount added varies with the ,15 natural brittleness of the film.

By softening agent as used in our process we mean those plasticizers capable of imparting softness to the film. The desired characteristics of the softening agent are that it shall be prac- 2O tically non-volatile at atmospheric pressure and room temperature, and that'it shall dry to a nonbrittle film in the presence of the main body of the vehicle. Examples of softening agents which may be used for our purpose are petroleum lubri- 5 eating oils and refined petroleum oils having a viscosity of 200 at 210 F. as determined with a Saybolt universal viscosimeter and also other materials such as butyl phthalate, ethyl abietate, tricresyl phosphate, castor oil, certain oil soluble phenol-aldehyde condensation products and the like. Plasticizers commonly used in the lacquer art to soften nitrocellulose films are operative.

It should be understood, however, that with any given drying oil, a softening agent must be selected that will be miscible with or soluble in said oil in order to produce a homogeneous solution.

As each drying oil and bronzing ink mixture requires a different amount of softening agent, it is impossible to specify generally the exact amounts of agents required. In some cases, it may be desirable to use mixtures of the different softening agents. In the use of the 200" viscosity petroleum oil as a softening agent, in conjunction with our novel rosin oil described in our copending application, Serial No. 581,506, filed of even date herewith, we may use from 10 to 30% by weight of the softening agent.

The only requisite in the addition or mixing of the softening agent with the drying oil is to insure that the softening agent is completely dissolved or dispersed in the drying oil.

The following example will serve to illustrate one specific phase of our invention. It is to be understood, however, that our invention is not limited thereby and is susceptible of wide variations and modifications. Parts given are parts by weight.

Example 100 parts of grade M wood rosin are heated together with 1 part of glycerine at a temperature of about 270 to 280 C. for a period of about 2 hours. 3 to 5 parts of dry natural fullers earth, such as Floridin A or B, coarse mesh, are now added, and the mixture is heated at a maximum of 300 C. for a period of 4 to 8 hours. At this time 10 parts of linseed oil are added and the heating is continued for 2 to 3 hours at the same temperature. During this treatment a distillate comprising about 8% by weight of the original rosin distills over. The distillate contains water of decomposition, together with other materials. The residual mass has an acid number 01' about 15. The mass is partially cooled, 25 parts of the 200" viscosity petroleum oil are added and the mixture is subjected to distillation under a vacuum of about 29 inches and at a temperature of about 150 to 200 0. (measured in the still). Distillation is continued until about 5% by weight of the mass is distilled off. The distillate constitutes a light oil and its removal increases the viscosity of the remaining mass and removes the objectionable odor. If desired, this light fraction may be separated from the main mass by steam distillation, at atmospheric pressure, and at a temperature of about 200 to 230 C. The residual mass in the still is next cooled and separated from the fullers eartlr.

The product is a viscous oil of reddish brown color by transmitted light and dark green by reflected light- It has no true boiling range at atmospheric pressure because heating to a distillation temperature will cause additional decomposition and destruction of the original product. The specific gravity is .97 to .98; acid number, below 10; saponification number to 25. Upon the addition of 05% of a cobalt dryer, the product will dry to a film with an increase in weight of about 7%.

In the above specific example, it is advantageous to add the petroleum oil prior to the final step of vacuum distillation as this insures the complete removal of any of the volatile constituents which may destroy the desired efiect.

In a similar manner to that indicated in the above example, other materials which lack many of the properties requisite to make them per- 5 7 Parts by weight Lake red C (dyestufDur 100 Blown linseed oil 150 Liquid drier (equivalent to 0.15 parts cobalt) This bronzing ink can be greatly improved and prepared at less cost by substituting 150parts by weight of the product obtained in the example for the 150 parts of linseed oil. Likewise cheap drying oils normally drying to produce brittle films may be substituted for the linseed oil with satisfactory results upon the incorporation of small amounts of plasticizers.

Many other variations may be practiced with 30 our invention without departing from thespirit thereof.

We claim as our invention:

A bronzing ink vehicle comprising a rosin oil having an acid number of about 15, and obtainable by heating rosinand an ester of a polyhydric alcohol at 270 to 300 C. for several hours in the presence of fullers earth, and from 10% to 30% of a substantially non-drying high boiling liquid as'a softening agent miscible there- 40 with and selected from the group consisting of high viscosity refined petroleum oils, liquid esters of phthalic acid, liquid esters of abietic acid, castor oil, and tricresy'l phosphate, the resulting mixture of said rosin oil and softening agent i5 drying to a non-brittle film.

ROBERT C. PALMER. PAUL O. POWERS. 

